Hello Diana, I am not a doctor, so I cannot answer the question we all ask ...,"when to start the Big 3?..." But matbe I can point you to a few resources to help.

Let's start by saying many here live for many years with a diagnosis of MAI/MAC/NTM who never get to the point where the antibiotics are required. For others, their overall symptoms and levels of infection are such that antibiotics are the immediate response. Then there is the great, gray "in between."

The experts constantly explore this subject. In 2020, guidelines for clinicians were issued, but it is pretty heavy reading:
https://ntminfo.org/wp-content/uploads/2020/07/NTMguidelines2020.pdf
For a more user-friendly explanation, see this YouTube Video from the National Jewish Health Patient Conference in 2022.

In addition to the vest, are you using airway clearance exercises to get the mucus out after it is loosened up? Do you use inhaled saline to make your lungs less welcoming to the bacteria?